1. Field of the Invention
This invention relates to an improved orthdontic face bow; and more particularly, to an orthodontic face bow having an inner wire which is provided with integral safety extensions projecting beyond the ends of the inner wire.
2. Description of the Prior Art
Orthodontic safety face bows are known in the prior art.
For example, Armstrong, U.S. Pat. No. 4,038,754 discloses a face bow having a pair of inner bow shank wires which are provided with guards adjacent the ends thereof. The guards are each comprised of a stop sleeve, a guard mounting sleeve welded to the stop sleeve and a shank wire having a loop formed at one end. The stop sleeve is positioned on the inner bow shank wire and the shank wire having the loop formed at one end is positioned within the guard mounting sleeve. The stop sleeve is secured to the inner bow shank by spot welding, soldering or crimping.
Andrews, U.S. Pat. No. 4,087,915 discloses a face bow having an inner wire with a pair of ends adapted for engagement with a pair of patient-mounted buccal tubes. The inner wire is provided with a pair of safety extensions for guarding the pair of ends. In one embodiment the safety extensions are each comprised of a crank-shaped wire having one portion extending beyond the inner wire end and a distal portion mounted to the inner wire apparently by soldering or welding. A pair of solder stops are provided on the inner wire for limiting entry of the inner wire ends into the buccal tubes. In another embodiment the inner wire is provided with a pair of coupling tubes adjacent each of the ends. A safety loop is provided for protecting each of the ends. The ends of the safety loops are captured within the coupling tubes. The coupling tubes are either soldered to, or left for slight movement on, the inner wire.
Thus, the Armstrong and Andrews safety face bows are of relatively complex construction each being comprised of a number of individual components which are held in place by soldering, spot welding and crimping. In practice, it has been found that the soldered, welded and crimped connections are unreliable and subject to breakage. Since exposure of the inner wire ends to contact with the user can cause grievous injury, it is most important that the safety mechanism be reliable and foolproof, thereby necessitating avoidance of unreliable solder and weld connections. Further, the use of extra components undesirably increases the weight of the face bow and makes the manufacture and assembly thereof more expensive and difficult.